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This paper proposes a novel highly reliable single-stage buck-boost inverter. It can be operated as grid-connected and stand-alone inverter. In a single-stage, it can generate an output ac voltage higher and lower than the input dc voltage. The proposed inverter can be employed in grid-connected single-phase PV systems without injecting large dc current into the grid. In addition, it has no shoot-through...
This paper proposes an ac-ac converter with bipolar voltage gain. It has both inverting and non-inverting operations. It has no shoot-through problem of voltage source or capacitor and can eliminate pulse-width modulation (PWM) dead-time between the switches, therefore high quality output ac power can be obtained and reliability of system can be improved greatly. The proposed converter can compensate...
The conventional structure of buck-boost inverter uses IGBTs. IGBTs have features like long tail current, fixed voltage drop and that is why its switching losses are high. In this paper switching cells structured buck-boost inverter is proposed. In switching cell structure, MOSFETs and external diodes with very fast reverse recovery characteristics are used, while the body diodes have no chance of...
Inverter is a definitive solution toward ac voltage regulation in a system having input dc voltage variation. This paper proposes, a novel single-stage single-phase buck-boost inverter called dual buck-boost inverter. It has the buck-boost function and requires only four active switches. It has no shoot-through worries and has improved reliability. In the proposed inverter, the body diodes of switches...
This paper presents a new type of cascaded PWM ac-ac converter with phase-shift PWM control. It can reach high output voltage by cascading single-phase units of low voltage rating devices. The proposed converter does not sense current/voltage polarity, and does not require current/voltage sensors and lossy snubbers for commutation, thereby the control complexity can be decreased. It has no shoot-through...
In this paper, a novel three-phase buck-boost ac-ac converter is proposed. It requires only three inductors and six switches. The proposed converter has no current shoot-through related problems and eliminates the PWM dead times, which results in greatly enhanced system reliability. The proposed converter allow the use of MOSFET without conducting body diode, therefore the reverse recovery issues...
The traditional hard switching bidirectional dc-dc converters cannot simply avoid the reverse recovery problem of MOSFET body diode, and they also require dead time between the switches to avoid current shoot-through. Therefore, the traditional bidirectional dc-dc converters are usually designed with IGBTs. The IGBTs have long tail current, low switching speed and fixed voltage drop when compared...
AC-AC converters based on Z-source networks have some unique advantages such as; provision of a wide range output voltage with both step-up and step-down capability, reversing or maintaining phase-angle, reducing the inrush and harmonic currents, and enhanced reliability. However, these existing Z-source ac-ac converters are non-isolated, and therefore, they need external bulky line frequency transformer...
Traditional non-isolated ac-ac converters require an external bulky line frequency transformer for electrical isolation and safety, for applications such as dynamic voltage restorers (DVRs) etc. This line frequency transformer has some demerits such as; high cost, large size, relatively high losses, saturation and start up inrush current. To overcome this drawback, an isolated buck type ac-ac converter...
In this paper, double step-down isolated ac-ac converters are proposed. The proposed converters have double step-down function and provides electrical isolation using high frequency transformer. The proposed converters avoid the saturation of transformer by adding a capacitor. In addition, the voltage stress of three bidirectional switches at the primary side of transformer is half of input voltage...
In this paper, buck and boost type AC-AC converters are proposed which are derived from the recently developed switching cell (SC) AC-AC converters. The volume of magnetic components of the SC AC-AC converters is large, and they are also associated with circulating current. The proposed AC-AC converters are free of circulating current and have smaller magnetic volume, therefore they can realize high...
In this paper, a dynamic voltage restorer (DVR) is presented based on a novel buck type PWM direct ac-ac converter topology. The ac-ac converter used in proposed DVR has no commutation problem because of using switch cell structure and coupled inductors, and therefore, it does not need to sense the input voltage polarity for safe commutation, which saves the cost of input voltage sensor. The proposed...
In this paper, a high-frequency isolated buck ac-ac converter is proposed using switching cell structure and coupled inductor, which is immune to damaging of switching devices because of open or short circuit problem. The proposed converter does not require any lossy RC snubber or sensing the input voltage polarity for implementation of dedicated soft commutation strategy, to solve the commutation...
The switching cell (SC) direct PWM ac-ac converters solve the commutation problem of traditional direct PWM ac-ac converters in a very effective way. The magnetic components of the SC ac-ac converters consist of two coupled inductors and an AC inductor. In order to make the SC ac-ac converters more useful and practical, this paper presents the integration of magnetic components in these converters...
In this paper, a new type of ac-ac converter is proposed which can operate as traditional non-inverting buck and boost converter or inverting buck-boost converter. The proposed converter is immune from shorting of voltage source even when all switches are turned on simultaneously, and therefore, PWM switching dead-times are eliminated to produce high quality output waveform. Owning to the benefit...
This paper proposes a novel three-phase PWM ac-ac converters, presents detailed circuit operation and operating principle. The proposed converters employs the basic switching cell structure and coupled inductor to solve commutation problem without sensing input voltage polarity. The commutation scheme allows that the proposed converters can be short and open circuited without generating high switch...
Spectral parameters such as the mean and median frequencies have been documented to be reliable outcome variables for the assessment of muscle fatigue. The objective of this paper is to examine young subjects' surface electromyography (EMG) signals at different levels of maximum voluntary contractions (MVC) and to analyze spectral shifts in mean and median frequencies (MNF, MDF). In this study, continuous...
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